Dynamic power supply sensor for multi-power supply applications

Abstract

In general, the subject matter described in this disclosure can be embodied in a system that implements power supply protection. The system includes first circuitry, second circuitry, a first power supply that is configured to power the first circuitry, and a second power supply that is configured to power the first circuitry and the second circuitry. The system also includes a power supply sensor including an input that is connected to the first power supply, and an output. The system also includes a hysteresis buffer including an input that is connected to the output of the power supply sensor, and an output that is connected to the first circuitry in a configuration that transitions the first circuitry to a protected state as a result of the hysteresis buffer transitioning output states.

What is claimed is: 
     
       1. A system that implements power supply protection, comprising:
 first circuitry; 
 second circuitry; 
 a first power supply that is configured to power the first circuitry, wherein the first power supply is configured to power the first circuitry through an arrangement in which the first circuitry is connected between a first potential provided by the first power supply and a reference potential; 
 a second power supply that is configured to power the first circuitry and the second circuitry, wherein the second power supply is configured to power the first circuitry through an arrangement in which the first circuitry is connected between a second potential provided by the second power supply and the reference potential, simultaneous with the first circuitry being connected between the first potential provided by the first power supply and the reference potential, the first potential being different from the second potential; 
 a power supply sensor including:
 (i) an input that is connected to the first power supply, and 
 (ii) an output; and 
 
 a hysteresis buffer including:
 (i) an input that is connected to the output of the power supply sensor, and 
 (ii) an output that is connected to the first circuitry in a configuration that transitions the first circuitry to a protected state as a result of the hysteresis buffer transitioning output states, wherein the hysteresis buffer is arranged to transition the first circuitry to the protected state as a result of the input of the hysteresis buffer receiving, from the output of the power supply sensor, a signal indicating that power provided to the input of the power supply sensor by the first power supply has decreased. 
 
 
     
     
       2. The system of  claim 1 , wherein the hysteresis buffer is configured to generate digital output signals from analog input signals received at the input to the hysteresis buffer. 
     
     
       3. The system of  claim 2 , wherein the hysteresis buffer includes a Schmitt trigger. 
     
     
       4. The system of  claim 1 , wherein the first power supply is configured to not power the second circuitry. 
     
     
       5. The system of  claim 1 , wherein a potential of the first power supply is independent from a potential of the second power supply. 
     
     
       6. The system of  claim 1 , wherein the power supply sensor comprises a diode-resistor network. 
     
     
       7. The system of  claim 1 , wherein the power supply sensor comprises a resistor-divider network. 
     
     
       8. The system of  claim 1 , wherein:
 the first circuitry includes a first sub-circuit block of a particular circuit; and 
 the second circuitry includes a second sub-circuit block of the particular circuit. 
 
     
     
       9. The system of  claim 1 , wherein the signal indicating that power provided to the input of the power supply sensor by the first power supply has decreased comprises the signal indicating that potential provided to the input of the power supply sensor by the first power supply has decreased. 
     
     
       10. The system of  claim 1 , further comprising a bias circuit switch providing at least part of a connection between the output of the hysteresis buffer and the first circuitry. 
     
     
       11. The system of  claim 10 , wherein the bias circuit switch is configured to set a DC operational value of the first circuitry as a result of an input of the bias circuit switch receiving a transition between output states from the hysteresis buffer. 
     
     
       12. The system of  claim 10 , wherein the bias circuit switch is configured to interrupt bias current provided to the first circuitry to provide improved voltage tolerance when no current is present through a circuit component of the first circuit. 
     
     
       13. A system that implements power supply protection, comprising:
 first circuitry; 
 second circuitry; 
 a first power supply that is configured to power the first circuitry; 
 a second power supply that is configured to power the first circuitry and the second circuitry; 
 a power supply sensor including:
 (i) an input that is connected to the first power supply, and 
 (ii) an output; 
 
 a hysteresis buffer including:
 (i) an input that is connected to the output of the power supply sensor, and 
 (ii) an output that is connected to the first circuitry in a configuration that transitions the first circuitry to a protected state as a result of the hysteresis buffer transitioning output states; and 
 
 a bias circuit switch providing at least part of a connection between the output of the hysteresis buffer and the first circuitry. 
 
     
     
       14. The system of  claim 13 , wherein the bias circuit switch is configured to set a DC operational value of the first circuitry as a result of an input of the bias circuit switch receiving a transition between output states from the hysteresis buffer. 
     
     
       15. The system of  claim 13 , wherein the bias circuit switch is configured to interrupt bias current provided to the first circuitry to provide improved voltage tolerance when no current is present through a circuit component of the first circuit. 
     
     
       16. The system of  claim 13 , wherein the first power supply is configured to not power the second circuitry. 
     
     
       17. The system of  claim 13 , wherein the power supply sensor comprises a diode-resistor network. 
     
     
       18. A power supply detector, comprising:
 a diode connected to a first power supply; 
 a resistor connected between the diode and ground; 
 a hysteresis buffer including an input that is connected between the diode and the resistor; and 
 a current bias switch including:
 (i) an input that is connected to an output of the hysteresis buffer, and 
 (ii) an output that is connected to a protected circuit and that is configured to drive an operational DC level of the protected circuit to different states based on a signal received at the input of the current bias switch from the output of the hysteresis buffer. 
 
 
     
     
       19. The power supply detector of  claim 18 , wherein the hysteresis buffer includes a Schmidt trigger. 
     
     
       20. The power supply detector of  claim 18 , wherein the current bias switch is powered by a different power supply than the first power supply.